1. Field of the Invention (Technical Field)
The present invention relates to direct gas-to-liquid pump apparatuses and methods.
2. Description of Related Art
Hydraulic ram pumps have been used for many decades to pump small volumes of water to high pressures utilizing large volumes of water from low-pressure sources. In the process, much of the low-pressure water is discarded. More recently steam and other vapors have been proposed to pump water or other liquids directly. Petichakis in U.S. Pat. No. 5,865,086 discloses a method in which high-pressure steam is introduced into the top of vertical cylinders filled with a liquid. The steam forces the liquid out the bottom of the cylinder. This can serve as a pump to move the liquid to a desired destination, or the liquid can be used to drive a turbine to generate electricity.
Johnson in U.S. Pat. Nos. 5,461,858, 5,551,237, and 5,713,202 describes a method of utilizing combustion gases from a power plant to drive water out of vertical cylinders, and the water is used to drive a turbine to generate electricity. Kershaw in U.S. Pat. No. 6,182,615 describes a method in which combustion gases are ignited above a liquid in a tank to drive the liquid out to a storage tank from which the liquid flows to a turbine to generate electricity.
The advantage of these inventions is that they can use pressurized gases in order to pump liquids directly without pistons, turbines, and gearboxes.
The main problem with these and other patents that utilize a gas or vapor to push a liquid out of a tank is that they inefficiently use the energy in the gas. For example, in U.S. Pat. No. 5,865,086, steam at constant pressure forces the liquid out of a cylinder. At that point, most of the energy is still in the high-pressure steam. When a valve is opened to release the steam, the energy of expansion of the steam is lost. The thermal efficiency of this system is about 10% even when the steam temperature is high. In U.S. Pat. No. 6,182,615, the combustion gases expand to force the liquid out of the cylinder, but the pressure in the storage tank must be considerably less than the maximum pressure of the combustion gases. If the pressure in the storage tank is high, only the high-pressure portion of the combustion expansion will be effective, and the efficiency will be low.
Coster in U.S. Pat. No. 1,055,880 and Tobber in U.S. Pat. No. 4,201,049 describe systems in which slugs of liquid are accelerated by gases to directly turn a turbine. Neither patent describes a method for pumping the liquid to high pressures. In both designs, no provision is made for Taylor instabilities at the gas-liquid interface or for heat loss from the gases to the liquid.
The present invention solves the above problems and greatly increases the efficiency of direct gas-to-liquid pumps utilizing energy from the constant pressure portion of the cycle and then utilizing the adiabatic expansion portion of the cycle. With the invention, the pumped liquid can be at higher pressure than the pressure of the gas. This is done by having a mass of liquid and possibly solid objects in an acceleration tube that are driven by the gas. The force from the gas imparts kinetic energy to the moving mass during a free run through the tube. When the mass of liquid comes to the end of the tube, it strikes a check valve, which is forced open to allow the liquid to enter a high-pressure region. Since the liquid is almost incompressible, if it has high velocity, it can build up high pressures when it is suddenly decelerated. This pressure can open a check valve that is backed by high-pressure gas.